Researchers report that an early test of an experimental vaccine for norovirus -- the cause of a stomach sickness that fells scores of cruise ship passengers and nursing home residents, among others -- reduced symptoms of vomiting and diarrhea by 52 percent.

Every year, norovirus sickens 19 million to 21 million Americans -- or one in 15 -- and kills as many as 800, according to the U.S. Centers for Disease Control and Prevention.

"Early results of testing an experimental vaccine for norovirus appear positive, providing optimism that a vaccine can be developed for this common cause of gastroenteritis," said lead researcher Dr. David Bernstein, a professor of pediatrics at Cincinnati Children's Hospital Medical Center and the University of Cincinnati.

"More testing will be necessary to ensure the vaccine is safe and effective," he said. "If this can be duplicated in larger trials, it could lead to the availability of a new vaccine for a very common illness."

The results of the study were to be presented Friday at ID Week 2013, the infectious diseases society conference in San Francisco.

Currently, there is no treatment or cure for the highly contagious virus, the most common cause of viral gastroenteritis in children and adults.

Outbreaks occur in close quarters, such as health care facilities, child care centers, schools and military bases in addition to cruise ships, the researchers said.

The vaccine might be useful for people in any of those settings, Bernstein said. Ocean-going travelers, for instance, could add the vaccine to their to-do list before departure.

But first, Bernstein hopes to test the vaccine in a larger "real-world" trial.

Dr. Jesse Reeves-Garcia, chief of the division of gastroenterology at Miami Children's Hospital, said the idea of a vaccine for norovirus is "fascinating."

"Norovirus ruins people's lives," he said. "They take a vacation, they take a cruise and spend three of four days in the toilet puking or pooping or both," he said.

A vaccine that's effective, safe and reasonably priced would be "great," Reeves-Garcia said. "It would be another sickness that I wouldn't see anymore."

Norovirus can spread through infected food or water, contaminated surfaces and even through the air.

Not everyone exposed to norovirus gets infected, and of those who are infected not all get sick, Bernstein said. But it is very common and can be serious, particularly for young children and older adults, he added.

A recent study found the overall cost of the disease in the United States is $5.5 billion a year, the researchers noted.

For the latest study, Bernstein's team randomly assigned 98 people, who agreed to drink water laced with the virus, to an injection of the vaccine or placebo.

Among those given the vaccine, 26 were infected as were 29 in the placebo group. Ten people in the vaccinated group had mild, moderate or severe vomiting and/or diarrhea compared with 20 in the non-vaccinated group -- a 52 percent reduction in symptoms.

The vaccine disarms two genotypes of norovirus, one of them the leading cause of U.S. outbreaks, the study authors say.

Data and conclusions presented at meetings are typically considered preliminary until published in a peer-reviewed medical journal.